Dads count too!

Today it seems obvious that a woman's health directly impacts the well-being of her future child. Women thinking about becoming pregnant — or those who already are — are often careful not to smoke, drink or take certain drugs. Meanwhile, conventional wisdom says that a father's health can't have any direct impact on that of his child. But as described in the cover story of the January/February issue of Miller-McCune, conventional wisdom is wrong: Fathers do matter.

The article surveys the science on the developmental consequences of paternal exposure to chemicals, focusing on pharmaceuticals like morphine and certain chemotherapies. Surprisingly, it turns out that if you dose a male rat with these substances, and then later — after the drug has had ample time to leave the animal's system — you have that rat mate, its progeny lag behind those of unexposed males in development. And, as you can probably guess since I'm writing about here in GroundTruth, these types of male-line trans-generational effects have been seen for pesticides too.

It's long been known that pesticides can damage men's reproductive ability. The classic example is Dow's fumigant Nemogen (DBCP), which sterilized workers in the California factory where it was produced and in the Nicaraguan banana plantations where it was heavily applied. Exposure to DDT and current-use pesticides like atrazine and diazinon has also been shown to harm sperm counts.

The idea that's only beginning to get a foothold is this: In addition to reducing or eliminating the viability of a man's sperm, pesticide exposure can damage the health of a man's children. Studies of farmers have found that fathers' pesticide exposure can increase the risk of miscarriage, premature delivery and childhood leukemia. A study of lab rats found that males exposed in the womb to the fungicide vinclozolin grew up to have reduced sperm counts. The male offspring of these animals also had reduced sperm counts and so did males in the next generation.

How these trans-generational effects are passed from father to son or daughter is not precisely known. The traditional "Biology 101" explanation — mutations in sperm DNA that are passed on to offspring — is probably at work some of the time. But the newly discovered alternative mechanism of epigenetic modification also appears to be a factor. One thing is clear, though: A man's chemical exposure plays an important role not only in his reproductive success, but also in the health of his future children.